### The relationship between the number of poles and the speed of an asynchronous motor

Date：2023-08-22 Author：XINDA MOTOR

_{1}of the rotating magnetic field of the stator , n

_{1}=60f/P, where n

_{1}is the synchronous speed in r/min; f is the AC power frequency in Hz; P is the number of pole pairs of the motor.

_{1}=3000/P. It can be seen that the more the number of magnetic pole pairs, the lower the rotational speed of the rotating magnetic field.

_{1}=3000 r/min ;

_{1}=1500 r/min ;

_{1}=1000 r/min ;

_{1}=750 r/min ;

_{1}=600 r/min .

_{1}of the stator's rotating magnetic field , because if n=n

_{1}, there will be no relative motion between the rotor and the stator's rotating magnetic field, and there will be no induced electromotive force and induced current in the rotor winding, and the rotor cannot be driven to rotate The electromagnetic torque, so there is a difference between the rotor speed n and the stator rotating magnetic field speed n

_{1 in the operation of the asynchronous motor, and the name "asynchronous" comes from this.}

_{Direct}Affect the working state of the asynchronous motor. The speed difference is represented by slip s: s=(n

_{1}-n)/n

_{1}.

_{1 , the rotor of the motor has not yet rotated due to mechanical inertia, the instantaneous speed of the rotor is n=0, (n }

_{1}-n)=n

_{1}, and the slip s=1; the rotor turns Afterwards, n>0, (n

_{1}-n)<n

_{1}, slip s<1; the rotor rotates with load, there must be enough electromagnetic torque to overcome the resistance torque, and only the rotor speed n is low At the speed n

_{1}of the stator rotating magnetic field, the relative motion between the rotor and the stator rotating magnetic field can generate a sufficiently large induced electromotive force and induced current to generate a sufficiently large electromagnetic torque. At this time (n 1 -n)

_{>}0, the rotation The difference rate s>0. Therefore, when the asynchronous motor is running normally, 0<s<1. Under rated load operating conditions, s is about 0.01~0.06.

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_{1}, that is, n=(1-s)×60f/P, where n is the speed in r/min; f is the AC power frequency in Hz; s is Slip rate; P is the number of pole pairs.